Fish oil is a rich source of omega-3 fatty acids, which may help lower blood pressure and protect the heart from disease. Fish oil is also used to treat a number of medical conditions, including depression, some eye diseases and premenstrual syndrome. Many of these uses are unproven. Fish oil can cause some side effects and may increase the risk of problems when combined with certain medications. Talk to your doctor before taking fish oil supplements.
Blood Thinners
Taking more than 3 g per day of fish oil may impair your blood's ability to clot properly and increase the risk of bleeding problems, according to MedlinePlus. For this reason, you should be cautious about combining blood thinners or antiplatelet drugs with fish oil. Drugs in this category include the blood thinners warfarin and heparin, aspirin, clopidogrel, dalteparin, dipyridamole, enoxaparin and ticlopidine. Talk to your doctor or pharmacist before taking fish oil if you are on any of these medications. Some supplements may also act like blood thinners and should not be combined with fish oil. These include angelica, clove, garlic, ginger, ginkgo, ginseng, red clover, turmeric and willow.
Estrogens
Talk to your doctor before combining estrogen-containing medications, such as hormone replacement therapy or birth control pills, and fish oil pills. This is a particular issue if you are taking fish oil to lower your blood triglyceride levels, a fat that, like cholesterol, can build up and block arteries. Birth control pills may impair the ability of fish oil to lower triglycerides, according to MedlinePlus. Drugs in this category include ethinyl estradiol and levonorgestrel.
High Blood Pressure Medications
Because fish oil may lower blood pressure, you should be careful about taking it with drugs to lower blood pressure, because it may cause too steep a drop in blood pressure, which can be dangerous. Drugs in this category include beta-blockers like atenolol, carvedilol, labetalol, metoprolol, propranolol, sotalol and timolol; diuretics, or water pills, like chlorothiazide, hydrochlorothiazide, chlorthalidone, indapamide, metolazone; captopril; enalapril; losartan; valsartan; diltiazem; amlodipine and furosemide. Don't combine fish oil with a blood pressure drug without talking to your doctor; he may want to monitor your blood pressure and make adjustments, if necessary.
Weight-Loss and Diabetes Medications
If you take the weight-loss drug orlistat, which blocks the absorption of fat, it may impair your body's ability to absorb fish oil. Taking fish oil and orlistat at least two hours apart may prevent the problem. Fish oil may increase blood sugar levels, so talk to your doctor before combining diabetes medications with fish oil, because your doctor may have to adjust your medication.
Positive Interactions
On a positive note, fish oil may reduce the risk of ulcers from non-steroidal anti-inflammatory drugs like ibuprofen and naproxen, as well as the side effects of the organ transplant drug cyclosporine. Fish oil may also increase the effectiveness of cholesterol-lowering medication and certain drugs used to treat psoriasis.
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